Fosinopril sodium is a medicinal compound useful as an antihypertensive agent. Its ability to inhibit the angiotension converting enzyme and thus lower blood pressure is disclosed in U.S. Pat. No. 4,337,201.
U.S. Pat. No. 5,006,344 explains that tablets comprising fosinopril sodium are relatively unstable when the tablets also comprise magnesium stearate as the lubricant. This patent further discloses that tablets with improved stability can be obtained by eliminating magnesium stearate and instead using as the lubricant either sodium stearyl fumarate or hydrogenated vegetable oil.
Sodium stearyl fumarate is said to be preferred since hydrogenated vegetable oil can cause processing problems of sticking to the punch tips (i.e. inadequate lubrication) during long tabletting runs.
Tablets comprising fosinopril sodium are now sold in the United States under the tradename Monopril™. These tablets are made in accordance with the teaching of U.S. Pat. No. 5,006,344 and comprise sodium stearyl fumarate as the lubricant.
While sodium stearyl fumarate appears to be an effective lubricant for fosinopril sodium tablets, it is much more expensive than other lubricants and is not commonly used.
The object of the present invention is thus to find a lubricant for fosinopril sodium tablets other than sodium stearyl fumarate, that is effective as a lubricant, and that is relatively inexpensive.